[WebView] Add a new flushVisualState API to AwContents.

content/public/browser/render_frame_host.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_PUBLIC_BROWSER_RENDER_FRAME_HOST_H_
 #define CONTENT_PUBLIC_BROWSER_RENDER_FRAME_HOST_H_
 
 #include <string>
 
 #include "base/callback_forward.h"
@@ skipping 75 matching lines @@
   virtual void AccessibilitySetTextSelection(
       int acc_obj_id, int start_offset, int end_offset) = 0;
 
   // This is called when the user has committed to the given find in page
   // request (e.g. by pressing enter or by clicking on the next / previous
   // result buttons). It triggers sending a native accessibility event on
   // the result object on the page, navigating assistive technology to that
   // result.
   virtual void ActivateFindInPageResultForAccessibility(int request_id) = 0;
 
+  // Roundtrips through the renderer and compositor pipeline to ensure that any
+  // changes to the contents resulting from operations executed prior to this
+  // call are visible on screen. The call completes asynchronously by running
+  // the supplied |callback| with a value of true upon successful completion and
+  // false otherwise (when the frame is destroyed, detached, etc..).
+  typedef base::Callback<void(bool)> FlushVisualStateResultCallback;
+  virtual void FlushVisualState(
+      const FlushVisualStateResultCallback& callback) = 0;
+
   // Temporary until we get rid of RenderViewHost.
   virtual RenderViewHost* GetRenderViewHost() = 0;
 
   // Returns the ServiceRegistry for this frame.
   virtual ServiceRegistry* GetServiceRegistry() = 0;
 
  private:
   // This interface should only be implemented inside content.
   friend class RenderFrameHostImpl;
   RenderFrameHost() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_RENDER_FRAME_HOST_H_